花生A08连锁群上含油量主效QTL（qOCA08）的精细定位

Increasing oil content is one of important targets for peanut breeding. But lack of superior high-oil germplasm and weakness of studies in genetic basis for oil content, lead to little progress in high-oil breeding. Previously, a major QTL(qOCA08) which could be repeatedly detected in three-year trials, was located on genetic linkage group A08 using a RIL population. The interval of this QTL is 4.8 cM. In this project, a individual plant which carries heterozygous target loci, is selected from the RIL population (F6) through molecular markers. And two NILs with different oil content are obtained from the self-cross progenies of this individual plant. Filial generation of two NILs is used to construct secondary segregation population. Then polymorphism SNP markers developed from resequencing analysis of two NIL genomes, are used to analyze genotype of secondary segregation population. Combining genotyping and phenotyping data, fine mapping of target QTL could be done through substitution mapping strategy. Finally transcriptome sequencing of two NILs with different oil content are performed to predict oil related candidate genes, and markers tightly linked with oil content could be developed based on results of fine mapping. This project could reveal genetic basis of oil content in peanut, and provide theoretical and material supports for promoting selection efficiency of high-oil germplasm.

提高含油量是我国花生育种的重要目标之一。由于优良稳定高油种质的缺乏和含油量遗传基础研究的薄弱，导致我国花生高油育种进展缓慢。在本项目前期研究中，利用重组自交系(RIL)群体，在A08连锁群上定位到一个连续三年稳定遗传的含油量主效QTL(qOCA08)，该QTL区间为4.8cM。在此基础上，本项目拟通过标记筛选该RIL群体(F6)中目标区段杂合单株，从其后代分离获得目标位点等位纯合的高油和低油两个近等基因系(NIL)，杂交后代构建次级分离群体；通过对两个NILs基因组重测序，开发多态性SNP标记；鉴定次级分离群体SNP标记基因型，结合表型数据，采用代换作图策略精细定位目标QTL；对高油和低油两个NILs材料开展转录组测序，预测含油量相关候选基因，开发紧密连锁的分子标记。本项目的开展，将为揭示花生含油量的遗传基础和提高高油种质的选择效率，提供理论依据和材料基础。

针对花生高油品种含油量相对较低且不稳定以及含油量遗传基础研究薄弱的问题，利用重组自交系群体和近等基因系及次级分离群体开展了研究工作。对重组自交系群体多环境测试发现含油量性状同时受到环境和基因型的影响，其广义遗传率为0.84。利用简化基因组测序鉴定群体家系基因型，构建了一张包含2595个SNP标记的高密度遗传连锁图谱。遗传图谱总长为2456.52 cM,标记平均密度为0.95 cM,大约可以覆盖80%的基因组区段，与物理图谱具有良好的共线性。结合表型和SNP遗传图谱信息,证实qOCA08是一个多环境稳定主效的含油量QTL,其遗传解释率为10.14%-27.19%,LOD值为4.83-14.35。利用重组自交系的残余杂合构建了精细定位分离群体，并针对目标区段加密了7个SNP标记。分析分离群体重组交换单株基因型和含油量表型，将qOCA08定位区间缩小至标记V000884和V000956之间的0.7 Mb区段。根据定位区间开发紧密连锁的高油标记，并在资源材料中证实该标记可提高四个百分点的含油量。双亲基因组重测序发现目标区间内有1个候选基因的的UTR区域存在插入缺失，有3个候选基因发生非同义突变。转录组测序显示有一个候选基因在高油和低油双亲存在差异表达。进一步对候选基因图位克隆和功能验证将加强花生含油量遗传研究基础，并有助于指导高油分子标记辅助选择技术的开发。